A Practical Guide

to hurricane tracking and plotting

Welcome to the practical guide to hurricane plotting and tracking, filled with tid-bits and other miscellaneous information. Here you may find the answer to a lot of your trivial (but oh so frustrating when you can't find the answer) questions. Somewhere else on our website we have information available on the current situation in the Caribbean. Our special local hurricane correspondents report from the Caribbean Islands about the situation with regards to threatening tropical systems. Reliable reports from the people who are in the middle of it all! For the latest advisories and satellite images see our Quick Hurricane Web Resource Locator, which will help you find the least overloaded web-server. Comments can be addressed to Gert van Dijken, site maintainer.

Tracking and plotting the coordinates of the current position and its forecast of hurricanes is fun (as long as the eye stays away...)! But sometimes confusing! Those advisories from the National Hurricane Center use all those different units; knots, kilometers, miles, nautical miles, etc. Not sure about how many nautical miles are in a kilometer? Or how knots relate to miles per hour? And how can I calculate without too much work how far a storm is located from the Caribbean Islands.

When are they going to use your name for a Hurricane? Who came up with the titles of the National Hurricane Advisories; WTNT32.KNHC, MIASPFAT3, what do they mean? And then you've been looking at the strike probabilities of the storm, but the advisories are using those strange abbreviations, which island is TDPR or what's the code for St.Martin?

More questions. When is a tropical system a tropical storm and when becomes it a Category 3 hurricane? Will my mobile home survive this storm?

These facts are so trivial, but sometimes so hard to find. Very annoying when you are tracking and plotting Hurricane Edouard, Fran, Hortense or whoever. This page should give you the answers to these questions, and more...

Also, don't miss the feature about the Hurricane Hunters. These brave guys fly right into the eye of a hurricane to get the valuable data for hurricane forecasting! It is written by Martha Watkins Gilkes, and was published in the LIAT Islander Inflight Magazine.

Hurricane Names

Wondering when they are going to use your name for a tropical system? If they haven't used it in the last 6 years, the chance is pretty small that they ever will. This because hurricane names are recycled every 6 years. So the list of names for 1996 will be used again in 2002. However, often the names of some famous hurricanes have been dropped and replaced with something else. E.g. Luis has been replaced by Lorenzo and Andrew by Alex. It's likely that 1998 storms Georges and Mitch will become 'classics' as well. The names for the Atlantic are:

How close is it? and How close can it get?

There is a storm brewing out there in the Atlantic, and you are wondering "How close is it?". Now you can accurately calculate the distance between the eye of the hurricane and your island. Just select your island and hurricane specifics like, the latitude and longitude coordinates of the storm and click on 'Show me how close...'. If your island is not listed you can enter your own coordinates.

In addition, you can enter the forward speed at which the hurricane is moving to calculate the time before the eye makes landfall at your location. If you know how far tropical storm winds extend from the center of the storm you can enter those as well to calculate how much preparation time you have left before winds will be blowing at tropical storm force. Caution: the numbers you get will only be true if the hurricane will travel in a straight line to your island at a constant speed and when you assume that the wind field doesn't change, in other words doesn't strengthen or weaken, over that time [this is normally not the case!!!].

Another tool available on this website calculates the closest point of approach of the eye of the storm to where you live from the 5-day forecast issued by the National Hurricane Center.

Select your Island:

Enter Hurricane Specifics:
The eye is located at:
It is moving near
TS winds extend from the center about

Or enter your Coordinates:
Lat:
Lon:

Help? The latitude/longitude location of the center of the storm and the speed at which it is moving can be found in the Public Advisories. A 72 hour forecast of the wind radii are listed in the Marine Advisories. Often it might be better to take the 72 hour value for wind radius to account for changes in hurricane strength. Both products are issued by the National Hurricane Center and linked directly from the Quick Hurricane Web Resource Navigator (QHWRN). Note that the units in the Public Advisories are normally in miles and mph (miles per hour), and in the Marine Advisories in nm (nautical mile) and kt (nautical mile per hour). Lat/Lon should be entered in decimal degrees, not in the dd:mm:ss-format, so: 18.5, not: 18:30:00. Valid range: latitude 0-90 degrees, longitude: 0-180 degrees. When numbers are entered in the 'Or enter your Coordinates' box, the island selection is ignored. The coordinates for the islands are based on the corresponding National Weather Service weather stations. The algorithm and code for the distance calculation was provided by the National Geodetic Survey.

Unit Conversion

one kilometer (km):

0.62 mile

0.54 nautical mile

one mile (m):

1.61 kilometer

0.87 nautical mile

one nautical mile (nm):

1/60 degree latitude

1.85 kilometer

1.15 mile

one knot (kt):

one nautical mile per hour

1.85 km per hour

1.15 mile per hour (mph)

Use the following table for a quick estimate of travel time of a tropical system to the Leeward islands.

One degree longitude equals:

at latitude

nautical miles

miles

kilometers

0° N

60.0

69.2

111.3

15° N

58.1

66.8

107.6

17.5° N

57.3

66.0

106.2

20° N

56.5

65.0

104.7

Example: Suppose that the center of a tropical storm is located at 15° N, 40° W, moving at 18 mph.
Most easterly Leeward islands located at around 61° W. This is a distance of 61-40=21° longitude. At 15° N this equals to 21x66.8= 1403 miles. So it will take around 1403/18= 78 hours or a 3 days and 6 hours to reach the islands. This is a rough estimate because the center of the storm has to stay on the same latitude and keep travelling at the same speed. You can also use the above form to calculate the distance and ETA.

The logic of NHC-advisories titles

WTNT32.KNHC, MIASPFAT3, etc., what do they mean? Which is which?

There are two different formats of NHC-advisories titles in use: (1) WTNT##.KNHC and (2) something like MIATCPAT#.

(1) WTNT##.KNHC: the first number (#) indicates the kind of advisory, the second the storm number. Marine Advisories have number 2, Public Advisories 3, Tropical Cyclone Discussions 4, Strike Probabilities 7. At times Tropical Cyclone Special Updates are released, numbered 6.

The storm numbers are as follows: Edouard has number 5, Fran 1 and Gustav 2.

Example: WTNT75.KNHC are the strike probablilites for Edouard.

(2) MIA*-format: Marine Advisories are titled MIATCMAT, Public Advisories MIATCPAT, Tropical Cyclone Discussions MIATCDAT, and the Strike Probabilities MIASPFAT. These are all followed by the number of the storm (see above).

What time is it? Timezone confusion... UTC, AST, EDT?

Most advisories have the time in the local timezone of where the storm is, this can be AST, EDT,... Then on other advisories is just says something like 18:00 Z. That means 'Zulu' time, which is the same as Coordinated Universal Time (UTC), formerly known as Greenwich Mean Time (GMT). Below a quick reference table of some of the most common timezones used in the Caribbean and USA. Most islands are in the Atlantic Standard Timezone (AST) and do not observe daylight saving time (for a island-specific timezone list see: sizes.com).

How to read Marine Advisories and Reconnaisance Reports

The Marine Advisories give information about the current and forecasted windfield and sea conditions around the center of the storm. Important to check is that if a Hurricane does not make landfall to see how close it passes by.

An example of a small piece taken out of the Marine Advisory of Hortense of 11PM/Sep 11:

All numbers are in nautical miles (nm). One nm equals 1.15 mile. In the above example the diameter of the eye is 16 nm (18 miles). Maximum sustained winds near the center are 85 kts (98mph) with gusts to 121 mph (105kt). Now comes the interesting part. Up to 50 nm to the North East of the center 64 kt winds (hurricane force) occur, and up to 25 nm to the SE, SW and NW. Connecting those points will make a kind of 'crooked' circle around the center. The same goes for the 50 kt, 34 kt (tropical storm) and 12 ft seas. So you can see from these data that the storm is a-symmetrical and that the 'grunt' of the storm is on the North-Eastern side.

At the time of this advisory Turks Island was 35 miles (30 nm) to the West of the center, so they are just outside the range of (sustained) hurricane force winds. If they would have been to the North West of the center they would be in the range of 64 kt winds. Since there are gusts to 105 kt (121 mph) they will experience hurricane force winds from time to time.

From time to time the National Hurricane Center sends out reconnaisance airplanes to the eye of the storm. If you are a serious 'hurricane tracker' you must check out those Reconnaisance Reports. This document tells you exactly how to decode it. It was written by Chris Sells and forwarded to me by Chris Novy.

Weather Station Identifiers for most of the Caribbean Islands as reported in the NHC Strike Probabilities Advisories. A complete list of all weather stations around the world can be found on the National Weather Service website. You can also click on the station identifier to get the current weather conditions (if available) from the Internet Weather Source (NWS).

Shrubs and trees blown down; all signs down. Extensive damage to roofing materials, windows and doors. Complete failures of roofs on many small residences. Complete destruction of mobile homes. Flat terrain 10 feet of less above sea level flooded inland as far as 6 miles. Major damage to lower floors of structures near shore due to flooding and battering by waves and floating debris. Low-lying escape routes inland cut by rising water 3 to 5 hours before hurricane center arrives. Major erosion of beaches. Massive evacuation of all residences within 500 yards of shore possibly required, and of singlestory residences within 2 miles of shore. Example: Hurricane Andrew (1992)

Category Five - A Catastrophic Hurricane

Winds: equal or greater than 157 mph, 137 kts, 252 km/h

Minimum surface pressure: lower than 920 mbar

Storm surge: higher than 18 ft, 5.6 m

Shrubs and trees blown down; considerable damage to roofs of buildings; all signs down. Very severe and extensive damage to windows and doors. Complete failure of roofs on many residences and industrial buildings. Extensive shattering of glass in windows and doors. Some complete building failures. Small buildings overturned or blown away. Complete destruction of mobile homes. Major damage to lower floors of all structures less than 15 feet above sea level within 500 yards of shore. Low-lying escape routes inland cut by rising water 3 to 5 hours before hurricane center arrives. Massive evacuation of residential areas on low ground within 5 to 10 miles of shore possibly required. Example: Hurricane Camille (1969)

In case of emergency: the Amateur Radio Operators are standing by

When everything else fails... When one of the Caribbean Islands is under threat of a tropical system I publish eye-witness reports from our Special Hurricane Correspondents on the Caribbean Hurricane Network. These reports come in by e-mail. If there is a big hit, it will be very likely that power and phonelines will be down, so the chance will be quite small of getting those reports by e-mail (no power=no pc; no phone=no dial-up with modem to isp). This of course doesn't only affect me but all emergency workers. This works the other way as well, when power and phones are down, people in the affected areas have a hard time of getting timely information. This is the time when the Amateur Radio Operators come in. Radio waves will always travel when you have a generator or other kind of power backup. Irvine B. Niffikeer, one of my hurricane correspondents on Trinidad & Tobago, forwarded me the following information on how to catch the emergency reports:

In the event of a disaster -God forbid-, one can obtain information from Amateur Radio Operators in the West Indies on the following frequencies:

HF Frequencies

14.303 MHz - The International Assistance and Traffic Net (IATN). This is the International Extension of the National Traffic System of the American Radio Relay League (ARRL)

3.815 MHz - The Antilles Emergency and Weather Net. The Amateur radio operators will handle emergency messages out of the affected areas during the first 48 to 60 hours after a Disaster.

These Nets will operate on a 24 hour basis. Health and welfare messages will be handled when Public Facilities are restored.
Operators in affected areas will most probable be operating with battery
power and stations outside of the disaster areas should cooperate and do
not jam the system with calls. Please listen.
These persons should direct their calls to one of the Net Control stations.

VHF Frequencies

147.80 MHz -600 Repeater. This is the local National Emergency Management Agency Repeater.

These frequencies will be used if they are operational after a hurricane. If these repeaters fail to function after a hurricane, operators will use the output frequencies as simplex frequencies to communicate.
In addition to the above frequencies 147.500 MHz will also be used as a
simplex frequency.

Because of modern technology e.g. satellite pictures, one can tell in advance when a hurricane is likely to strike. In this situation, amateur radio operators will secure antennas and may shut down their stations about 1 hour before the hurricane strikes. During this period there will be
lightning and strong winds until the hurricane passes. This period can be 2 to 3 hours.

Only those stations that took the necessary precaution and preparation in time will be heard on the air.

I hope you find this information useful and informative so that people can be aware of what is likely to happen in the event of a National Disaster and will be more enlightened and cooperate when the real situation occurs -God forbid-.

National Hurricane Center Advisories are released at 03:00, 09:00, 15:00 and 21:00 GMT. Intermediate advisories are released at 00:00, 06:00, 12:00 and 18:00 GMT. GMT is 4 hours ahead of Eastern Daylight Time.

Hurricane Plotting Software and Tracking Charts:

JStrack - Freeware. Tcl/Tk-based Hurricane Tracking Program. Basic, just what you need, without all the frills! A great program! Developed by Jim Graham. It also includes filters to automatically process NHC advisories. Highly recommended.

Add any historical track to your own map with Google maps: stormadvisory.org. Very nicely done!

Hurricane - Fast, full featured hurricane tracking app for the iPhone and iPod Touch by Kitty Code.

MyHurricane.net - Hurricane tracking with model runs embedded in Google Maps. You can also click through the archived advisories of storms to see how well the forecast agreed with the actual track. Nice and clean interface.

Palm Beach Post, a lot to offer, like the latest hurricane related news. (Excellent site but why didn't they cut down on the large number of graphics and un-necessary java applets which really slows down browsing)